The present invention concerns, broadly, maneuvering large and heavy equipments onto and from the sea floor. More particularly, the invention concerns a support structure for use in drilling and completing subsea oil and/or gas wells and methods for installing the structure on and removing the structure from the sea floor. As drilling and production water depths increase beyond the point of optimum diver utilization placing such structures on and removing such structures from the ocean floor must be conducted remotely from a floating vehicle. Motions induced by wind, wave and current create vessel-equipment interactions which, if not properly controlled, can render conventional handling techniques worthless. In addition, such structure placement and removal operations should include utilization of a minimum number of marine vessels, the ability to work under normal weather conditions, a relatively rapid completion of the operations to preclude extended waits for lengthy periods of good weather, and the ability to place the structure in the correct geographical location and attitude. The structure should also be designed for easy installation, should be capable of withstanding the abnormal rigors of sea floor existence, and should be retrievable at the conclusion of its working life. The structure and methods of the present invention meets all of the aforementioned requirements.